This invention relates to a spray orifice and particularly to one adapted for discharging a mixture of atomized liquid entrained within a gas stream for coating a surface with the liquid.
Molding, casting and forming dies used in workpiece fabrication processes frequently require a very thin and uniformly distributed coating of a release agent on their forming surfaces to enable the workpiece to be easily removed from the machine. Typical devices for applying release agents have two primary components: a nozzle and an orifice. The nozzle component is a fluid control device which mixes together pressurized gas (typically air) and a liquid release agent. The orifice component releases the mixture in a controlled pattern which is directed at the surfaces to be coated. In some applications, the nozzle and orifice components are physically incorporated into a unitary assembly. In other applications, one or more orifices are remotely mounted from the associated nozzle and conduits are used to transfer the pressurized gas and liquid to the orifices.
In one type of presently available orifice, the mixture is discharged through an elongated laterally extending slot which produces a fan-shaped discharge pattern. Although presently available orifices of this type generally perform satisfactorily, designers are continually striving to improve their performance. Presently available orifices have a tendency to cause the finely atomized liquid entrained within the pressurized gas to "recoalesce" to form larger drops which are deposited in a non-uniform manner on the surface being coated. When applying die release agents, such uneven application may lead to uneven "spot" cooling of the die surfaces and additionally wastes release material.
The improved orifice in accordance with this invention provides finely divided, uniformly distributed spray of atomized liquid such as a die release agent. The present orifice includes an inside cavity in the form of a curved surface of revolution. The mixture is discharged from the orifice through a slot passing through the inside cavity having a minimum width at its lateral ends and an increasing width at its center. In addition, the thickness of the tip in the region surrounding the slot is of a substantially uniform thickness. These inventors have found that such design features reduce the likelihood of atomized liquid recoalescing to form large droplets, thus providing a highly uniform distribution of liquid in the discharged spray.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.